Once you finish both the “Proof of Guilt” and “Proof of Innocence” sidequests, the third “Proof of Justice” side story opens up in Octopath Traveler 2. As with all three of the others, it takes place at the Timberrain courthouse. However, for the first time players get to go inside after seeing Meylan is no longer in sight.
Judge Astell was murdered, and Meylan was the last person seen with him. Everyone assumes the courtroom guard did it. Meylan will be accused in the background, and you can talk to a Spectator to learn judges are trying to frame him and get the “Proof of Justice” side story.
You need to talk to some people in the courthouse before you set off. First, you need to use someone like Osvald to get information. If you Scrutinize the Clerk, you’ll get a hint about visiting his aunt in New Delsta. Then, talk to the Court Reporter on the right. The person will mention throwing a murder weapon in a lake, so it’d end up down the Southern Timberrain Trail and wind up in the ocean.
Since you’re right there, head to the South Timberrain Trail first. This is a “recommended level 45” area, so be careful if you’re at a lower level. Right after you get over the bridge, head slightly north to the pier so you can head across the river. Near the rainbow and waterfall, you should see the indicative blue blinking of a hidden item. That’s the Stolen Sword you need to help proof Meylan is innocent.
From there, head to New Delsta, then go to the New Delsta: Backstreets area. If you walk along the road heading to the Game Parlor, you’ll see a Dour Elderly Woman. That’s Meylan’s aunt. You’ll need to have someone like Osvald Scrutinize her or Hikari Bribe her. This will give you the information that is the second piece of evidence.
Head back to Timberrain with both the information and stolen sword, and tell the Spectator what you found during the day. Handing in these two items will end this “Proof of Justice” side story in Octopath Traveler 2. You’ll get 30,000 leaves, a Fortifying Nut (L), and a Magic Nut (L).
Octopath Traveler 2 is available for the Switch, PS4, PS5, and PC. A demo is available.
Related: Who is the Best Character to Start With in Octopath Traveler 2 on Attack of the Fanboy